Communication network system

ABSTRACT

A communication network system has a plurality of communication terminals, each having a first transmitting unit and a first receiving unit. Information is transmitted and received among the communication terminals through the first transmitting unit and the first receiving unit. At least two of the communication terminals are used as relay terminals. Each of the relay terminal has a second transmitting unit and a second receiving unit for performing only one-to-one-type communication. A received-information relay unit transmits information received from the first receiving unit to the second transmitting unit and transmits information received from the second receiving unit to the first transmitting unit. A relay-terminal-information transmitting unit transmits to the first transmitting unit ID information of the relay terminal and ID information of a terminal to which the relay terminal is providing relay services. A storage unit stores the information of the relay terminals and relay situations thereof from relay terminal information received from the first receiving unit. When the relay terminal discontinues the relay services, the presence or the absence of an available relay terminal is determined by referring to the storage unit. If there is an available relay terminal, an instruction is provided to the terminal which is receiving the relay services to change the relay terminal.

This application is based upon and claims the benefit of priority under35 USC §120 from U.S. Ser. No. 09/534,457, filed Mar. 27, 2000 now U.S.Pat. No. 6,693,875, and under 35 USC §119 from Japanese PatentApplication Nos. 11-091719, filed Mar. 31, 1999, the entire contents ofeach are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication network system in whichcommunication can be performed among a plurality of mobile terminals.

2. Description of the Related Art

Optical communication using infrared rays is being performed as a datacommunication interface for use in personal computers and mobileterminals including personal digital assistants (PDA). The infrared dataassociation (IrDA) protocol is a standard protocol for infrared opticalcommunications.

However, in infrared optical communication using this IrDA standardprotocol, only a one-to-one-type communication function is supported.Thus, when a single one-to-one-type communication terminal communicateswith a plurality of terminals connected via a local area network (LAN),it is necessary to connect at least one relay terminal having both theIrDA function and the LAN function to a LAN system circuit. Then,communication is performed via this relay terminal.

As in the IrDA communication interface, a data communication interfaceusing a modem connected to a telephone line also supports only aone-to-one-type communication function. Terminals using IrDA or a modemand merely having a one-to-one-type communication function arehereinafter referred to as “one-to-one-type communication terminals”.

Such a one-to-one-type communication terminal can communicate with aplurality of terminals by the provision of a relay terminal which relaysinformation of the one-to-one-type communication terminal to the otherterminals. However, the following problems are encountered if IrDA isused as a communication interface.

If the relay terminal or the one-to-one-type communication terminalusing IrDA is moved, the communication link may be disconnected. Whenthe relay terminal discontinues relay services, the one-to-one-typecommunication terminal is no longer able to communicate with the otherterminals.

However, even if the relay terminal is moved or the relay services arediscontinued, the provision of an extra relay terminal which takes overthe relay services in a network (LAN) makes it possible to continuerelaying information of the one-to-one-type communication terminal,which can thus communicate with the other terminals.

However, the one-to-one-type communication terminal is not disposed inthe network. It is thus impossible for the one-to-one-type communicationterminal to monitor the situations of the terminals connected to thenetwork nor can it check for the presence of another relay terminal inthe network even if it attempts to send a relay request to the relayterminal.

Similarly, in performing communication using a modem, problems similarto those presented by IrDA communication may be encountered if relayservices are discontinued or a telephone line is disconnected, therebydiscontinuing communications between a one-to-one-type communicationterminal using a modem and other terminals. There may be provided amechanism for indicating another relay terminal which takes over relayservices before the corresponding relay terminal discontinues the relayservices. Even in this case, if a communication link is accidentallydisconnected for a one-to-one-type communication terminal using IrDA, orif a telephone line is disconnected for a one-to-one-type communicationterminal using a modem, communication can no longer be performed.

Even if the relay services are successfully passed from one relayterminal to another relay terminal, the one-to-one-type communicationterminal first sends a connection request to the indicated relayterminal, and then, after a communication link is established, theone-to-one-type communication terminal is able to receive the relayservices. In other words, the one-to-one-type communication terminal isunable to receive information sent to this terminal until thecommunication link with the designated relay terminal is established.

Additionally, a one-to-one-type communication terminal using a modemcannot even be connected to a relay terminal while the relay terminalhas already started to provide relay services. If only one telephonenumber of the relay terminal is known to the one-to-one-typecommunication terminal, the terminal cannot even be connected to therelay terminal, thus failing to receive the relay services.

The aforementioned IrDA communication interface and the modems are majorcommunication interfaces for use in mobile personal computers and mobileterminals. Thus, the above-described problems are becoming serious asmobile computing is becoming widespread and is more commonly utilized.

Therefore, in communicating with a plurality of terminals via a relayterminal, even if a one-to-one-type communication terminal becomesunable to communicate with the relay terminal, the communication must becontinued by passing relay services from the relay terminal to anotherrelay terminal disposed in a network.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide acommunication network system which enables a one-to-one-typecommunication terminal connected to a communication network, such as aLAN, via a relay terminal to continue communicating with a plurality ofterminals disposed in the network by informing the one-to-one-typecommunication terminal of the presence of another relay terminal even ifa communication link with the relay terminal is accidentallydisconnected or relay services provided by the relay terminal arediscontinued, and which allows the one-to-one-type communicationterminal to continue receiving information from the other terminalswithout discarding it even before a communication link with the newlyindicated relay terminal is established.

In order to achieve the above object, according to one aspect of thepresent invention, there is provided a communication network systemincluding a plurality of communication terminals, each having a firsttransmitting unit and a first receiving unit, connected via atransmission channel. Information is transmitted and received among thecommunication terminals through the first transmitting unit and thefirst receiving unit. At least two of the communication terminals areused as relay communication terminals. Each of the relay communicationterminals includes a second transmitting unit for performing onlyone-to-one-type communication and a second receiving unit for performingonly one-to-one-type communication. A received-information relay unittransmits information received from the first receiving unit to thesecond transmitting unit and transmits information received from thesecond receiving unit to the first transmitting unit. Arelay-terminal-information transmitting unit transmits to the firsttransmitting unit terminal identification information of the relayterminal and terminal identification information of a terminal to whichthe relay terminal is providing relay services as relay terminalinformation. A relay terminal storage unit stores information of therelay terminal and another relay terminal and relay situations of therelay terminals from the relay terminal information received from thefirst receiving unit. Upon discontinuing the relay services by the relayterminal which is providing the relay services, the presence or theabsence of an available relay terminal is determined by referring to therelay terminal storage unit, and if there is an available relayterminal, an instruction is provided to the terminal which is receivingthe relay services to change the relay terminal.

With this configuration, even if a relay terminal discontinues relayservices, an available relay terminal in a network can take over therelay services, thereby enabling a one-to-one-type communicationterminal to continue communicating with the other terminals.

According to the aforementioned communication network system, therelay-terminal-information transmitting unit may have a function ofregularly transmitting the relay terminal information.

With this arrangement, a one-to-one-type communication terminal is ableto monitor the current relay situation of the relay terminals disposedin the network. Accordingly, even if a communication link isaccidentally disconnected, the one-to-one-type communication terminalsearches for another relay terminal without the need for the designationof another relay terminal from the current relay terminal, therebymaking it possible to continue receiving the relay services.

According to the aforementioned communication network system, upondiscontinuing the relay services by the relay terminal, the terminalwhich is receiving the relay services may change from the relay terminalto a subsequent relay terminal, and the subsequent terminal may thenstore received information until a connection is established with theterminal which is receiving the relay services.

With this arrangement, until a communication link is established betweenthe one-to-one-type communication terminal and the subsequent relayterminal which is to take over the relay services, the informationaddressed to the one-to-one-type communication terminal is received andstored by the subsequent relay terminal. Thus, the one-to-one-typecommunication terminal is able to receive information without losing it.

According to another aspect of the present invention, there is provideda communication network system including a plurality of communicationterminals, each having a first transmitting unit and a first receivingunit, connected via a transmission channel. Information is transmittedand received among the communication terminals through the firsttransmitting unit and the first receiving unit. At least one of thecommunication terminals is used as a central relay communicationterminal, and at least one of the communication terminals is used as arelay communication terminal. The relay communication terminal includinga second transmitting unit for performing only one-to-one-typecommunication and a second receiving unit for performing onlyone-to-one-type communication. A received-information relay unittransmits information received from the first receiving unit to thesecond transmitting unit and transmits information received from thesecond receiving unit to the first transmitting unit. Arelay-terminal-information transmitting unit transmits to the firsttransmitting unit terminal identification information of the relayterminal and terminal identification information of a terminal to whichthe relay terminal is providing relay services as relay terminalinformation. The central relay communication terminal includes arelay-terminal storage unit for storing information of the relayterminal and another relay terminal and relay situations of the relayterminals from the relay terminal information received from the firstreceiving unit. Thus, an available relay terminal can be designated to aterminal which makes a request to provide the relay services.

With this configuration, only the central communication terminalreceives a request for relay services from the one-to-one-typecommunication terminal. Accordingly, when a one-to-one-typecommunication function is implemented by using a modem, only onetelephone number is required for enabling the one-to-one-typecommunication terminal to receive the relay services.

According to the aforementioned communication network system, at leasttwo of the first transmitting units and at least two of the firstreceiving units may be provided.

According to the above-described communication network system, at leasttwo of the second transmitting units and at least two of the secondreceiving units may be provided.

According to the above-described communication network system, at leasttwo of the first transmitting units and at least two of the firstreceiving units may be provided, and at least two of the secondtransmitting units and at least two of the second receiving units may beprovided.

According to still another aspect of the present invention, there isprovided a communication network system including a plurality ofcommunication terminals, each having a first transmitting unit and afirst receiving unit, connected via a transmission channel. Informationis transmitted and received among the communication terminals throughthe first transmitting unit and the first receiving unit. At least twoof the communication terminals are used as relay communicationterminals. Each of the relay communication terminals includes a secondtransmitting unit for performing only one-to-one-type communication anda second receiving unit for performing only one-to-one-typecommunication. A third transmitting unit performs only one-to-N-typecommunication. A third receiving unit performs only one-to-N-typecommunication. A received-information relay unit transmits informationreceived from the first receiving unit to the second transmitting unitand to the third transmitting unit, and transmits information receivedfrom the second receiving unit to the first transmitting unit and to thethird transmitting unit, and transmits information received from thethird receiving unit to the first transmitting unit and to the secondtransmitting unit. A relay-terminal-information transmitting unittransmits to the first transmitting unit terminal identificationinformation of the relay terminal and terminal identificationinformation of a terminal to which the relay terminal is providing relayservices as relay terminal information. A relay terminal storage unitstores information of the relay terminal and another relay terminal andrelay situations of the relay terminals from the relay terminalinformation received from the first receiving unit. Upon discontinuingthe relay services by the relay terminal which is providing the relayservices, the presence or the absence of an available relay terminal isdetermined by referring to the relay terminal storage unit, and if thereis an available relay terminal, an instruction is provided to theterminal which is receiving the relay services to change the relayterminal.

According to a further aspect of the present invention, there isprovided a relay terminal for use in a communication network systemwhich includes a plurality of communication terminals, each having afirst transmitting unit and a first receiving unit, connected via atransmission channel. Information is transmitted and received among thecommunication terminals through the first transmitting unit and thefirst receiving unit. One of the communication terminals is used as therelay terminal. The relay terminal includes a second transmitting unitfor performing only one-to-one-type communication and a second receivingunit for performing only one-to-one-type communication. Areceived-information relay unit transmits information received from thefirst receiving unit to the second transmitting unit and transmitsinformation received from the second receiving unit to the firsttransmitting unit. A relay-terminal-information transmitting unittransmits to the first transmitting unit terminal identificationinformation of the relay terminal and terminal identificationinformation of a terminal to which the relay terminal is providing relayservices as relay terminal information. A relay terminal storage unitstores information of the relay terminal and another relay terminal andrelay situations of the relay terminals from the relay terminalinformation received from the first receiving unit. Upon discontinuingthe relay services by the relay terminal which is providing the relayservices, the presence or the absence of an available relay terminal isdetermined by referring to the relay terminal storage unit, and if thereis an available relay terminal, an instruction is provided to theterminal which is receiving the relay services to change the relayterminal.

According to a yet further aspect of the present invention, there isprovided a method for relaying information between a plurality ofcommunication terminals in a communication network system. At least twoof the communication terminals are used as relay communicationterminals. The method includes a first transmitting step, a secondtransmitting step, a storage step, a determining step, and a providingstep. In the first transmitting step, information received from onecommunication terminal is transmitted to another communication terminal.In the second transmitting step, terminal identification information ofthe relay terminal and terminal identification information of a terminalto which the relay communication terminal is providing relay servicesare transmitted as relay terminal information. In the storage step,information of the relay terminal and another relay terminal and relaysituations of the relay terminals are stored from the relay terminalinformation transmitted in the second transmitting step. In thedetermining step, the presence or the absence of an available relayterminal is determined by referring to the relay terminal informationstored in the storage step when the relay terminal discontinues therelay services. In the providing step, an instruction is provided to theterminal which is receiving the relay services to change the relayterminal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically illustrating the configurationof a relay terminal according to a first embodiment of the presentinvention;

FIG. 2 is a block diagram schematically illustrating the configurationof a one-to-one-type communication terminal according to the firstembodiment of the present invention;

FIG. 3 is a block diagram schematically illustrating the configurationof a LAN terminal according to the first embodiment of the presentinvention;

FIG. 4 illustrates the current relay situation in a network systemaccording to the first embodiment of the present invention;

FIG. 5 illustrates an example of the storage table of a relay terminalstorage unit according to the first embodiment of the present invention;

FIG. 6 is a block diagram schematically illustrating the configurationof a one-to-one-type communication terminal according to a secondembodiment of the present invention;

FIG. 7 is a block diagram schematically illustrating the configurationof a relay terminal according to a third embodiment of the presentinvention;

FIG. 8 illustrates an example of the storage table of a relay terminalstorage unit according to a third embodiment of the present invention;

FIG. 9 illustrates the current relay situation in a network systemaccording to a fourth embodiment of the present invention;

FIG. 10 illustrates an example of the storage table of a relay terminalstorage unit according to the fourth embodiment of the presentinvention;

FIG. 11 is a block diagram schematically illustrating the configurationof a central relay terminal according to the fourth embodiment of thepresent invention; and

FIG. 12 is a block diagram schematically illustrating the configurationof a relay terminal according to the fourth embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below through illustrations ofpreferred embodiments with reference to the drawings.

First Embodiment

As discussed above, there is conventionally provided a communicationnetwork system which enables multicast communication among a pluralityof terminals including one-to-one-type communication terminals usingIrDA or a modem by relaying information sent from and to theone-to-one-type communication terminals. In this system, however, if therelay terminal discontinues relay services, the one-to-one-typecommunication terminals are no longer able to communicate with the otherterminals.

In the present invention, the following type of communication networksystem is implemented in which a one-to-one-type communication terminalis able to continue communicating with other terminals, even if a relayterminal discontinues relay services, by connecting the one-to-one-typecommunication terminal to an extra relay terminal disposed in a network.

FIGS. 1 through 3 are schematic diagrams illustrating communicationterminals according to a first embodiment of the present invention. Thecommunication terminals are each formed of a user information processingunit 101 for running applications, and a communication control unit 102for controlling communication. FIG. 1 illustrates the configuration of arelay terminal; FIG. 2 illustrates the configuration of aone-to-one-type communication terminal; and FIG. 3 illustrates theconfiguration of a LAN terminal.

According to the relay terminal shown in FIG. 1, the communicationcontrol unit 102 includes a first transmitting unit 111, a firstreceiving unit 112, a second receiving unit 113, a second transmittingunit 114, a relay-terminal-information transmitting unit 115, aninformation transmitting unit 116, a relay terminal storage unit 117, arelay-terminal changing information transmitting unit 118, and areceived-information relay unit 119.

According to the one-to-one-type communication terminal illustrated inFIG. 2, the communication control unit 102 has the second receiving unit113, the second transmitting unit 114, the information transmitting unit116, and the received-information relay unit 0.119.

According to the LAN terminal shown in FIG. 3, the communication controlunit 102 is formed of the first transmitting unit 111, the firstreceiving unit 112, the information transmitting unit 116, and thereceived-information relay unit 119.

The basic functions of the above-described terminals are the same.However, the LAN terminal has only the first transmitting unit 111 andthe first receiving unit 112 as a means of communication, while theone-to-one-type communication terminal has only the second transmittingunit 114 and the second receiving unit 113 as a means of communication.

In the following description, a discussion is primarily given of therelay terminal shown in FIG. 1 having both functions provided for theLAN terminal and for the one-to-one-type communication terminal. Thefunctions of the LAN terminal and the functions of the one-to-one-typecommunication terminal overlap with those of the relay terminal, and anexplanation thereof will thus be omitted.

According to the relay terminal, the information transmitting unit 116of the communication control unit 102 supplies information to the firsttransmitting unit 111 or the second transmitting unit 114 and thesupplied information is transmitted therefrom. More specifically, theinformation transmitting unit 116 supplies transmission informationrequested by the user information processing unit 101 to the firsttransmitting unit 111 or the second transmitting unit 114.

The user information processing unit 101 serves as an informationprocessing function for running applications. Therelay-terminal-information transmitting unit 115 acquires from the relayterminal storage unit 117 information of a one-to-one-type communicationterminal to which the relay terminal is currently providing relayservices, and transmits terminal ID information of the relay terminaland terminal ID information of the above-mentioned one-to-one-typecommunication terminal to the first transmitting unit 111.

The first transmitting unit 111 serves as a fast communication unitimplementing a serial communication function for sending and receivingdata via a transmission channel. The first transmitting unit 111transmits information requested by the information transmitting unit116, the relay-terminal-information transmitting unit 115, or thereceived-information relay unit 119.

The second transmitting unit 114 may be provided with an infrared sourceand drives it according to supplied information so as to transmit aninfrared signal. In this case, the second transmitting unit 114 maytransmit information requested by the information transmitting unit 116,the relay-terminal changing information transmitting unit 118, or thereceived-information relay unit 119 by means of non-contactcommunication (wireless communication) using the infrared signal.Alternatively, the second transmitting unit 114 may transmit informationvia a modem, in which case, it may transmit information requested by theinformation transmitting unit 116, the relay-terminal changinginformation transmitting unit 118, or the received-information relayunit 119 through a telephone line via the modem.

The second receiving unit 113 may be provided with a photodetector forperforming photoelectric conversion. In this case, the second receivingunit 113 may convert an infrared signal received by means of non-contactcommunication (wireless communication) into an electrical signal andoutput it. Alternatively, the second receiving unit 113 may convertreceived information into an electrical signal and output it through atelephone line via a modem.

The first receiving unit 112 receives signals transmitted via a signaltransmission channel, and thus serves as a serial communication functionfor receiving data via the transmission channel. The first receivingunit 112 and the second receiving unit 113 send received information tothe received-information relay unit 119.

The received-information relay unit 119 has both functions ofidentifying the received information and transferring it. Morespecifically, if the information received from the first receiving unit112 or the second receiving unit 113 is relay terminal information, thereceived-information relay unit 119 sends this information to the relayterminal storage unit 117. If the received information is not relayterminal information but is addressed to the relay terminal itself, thereceived-information receiving unit 119 transfers the information to theuser information processing unit 101 and also to the first transmittingunit 111 or the second transmitting unit 114. If the receivedinformation is not addressed to the relay terminal, thereceived-information receiving unit 119 transfers the information not tothe user information processing unit 101 but to the first transmittingunit 111 or the second transmitting unit 114.

The relay terminal storage unit 117 has the function of registeringinformation of a one-to-one-type communication terminal to which therelay terminal is currently providing relay services and the function ofstoring a current relay situation. The current relay situation is storedby determining which relay terminal is providing relay services andwhich one-to-one-type communication terminal is receiving them accordingto the relay terminal information obtained from the received-informationrelay unit 119.

When the relay terminal discontinues relay services, the relay-terminalchanging information transmitting unit 118 sends ID information of anavailable relay terminal obtained from the relay terminal storage unit117 to the one-to-one-type communication terminal which is receivingrelay services.

In the communication network system according to the present inventionthrough illustrations of the following embodiments, it is assumed that awireless LAN is used as a core system and mobile terminals are primarilyused. However, the essence of the present invention is not altered evenif the present invention is applied to a cable LAN primarily havingfixed terminals or a LAN having both fixed terminals and mobileterminals. Additionally, the present invention is used in a LAN as anexample only, and it may be applied to another type of communicationnetwork other than the LAN.

In the communication network system constructed in accordance with thefirst embodiment, a method for registering information of aone-to-one-type communication terminal in the relay terminal storageunit 117 (i.e., for storing information to which one-to-one-typecommunication terminal the relay terminal is providing relay services)is discussed below with reference to FIG. 4.

In FIG. 4, eight terminals, such as C1, C2, Cs1, Cs2, Cs3, Cs4, Cc1, andCc2, are provided. Among these terminals, the terminals C1, C2, Cs1,Cs2, Cs3, and Cs4 form a LAN so that they can communicate with eachother.

The terminals Cs1, Cs2, Cs3, and Cs4 are configured, as shown in FIG. 1,and implement not only a serial communication function by beingconnected to a transmission channel forming the LAN, but also aone-to-one-type communication function by using IrDA or a modem.

The terminals C1, C2, Cs1, Cs2, Cs3, and Cs4 are connected to atransmission channel L forming the LAN, thereby implementing a serialcommunication function of sending and receiving data via thetransmission channel L. However, the terminals C1 and C2 do not have aone-to-one-type communication function implemented by using IrDA or amodem. The terminals Cc1 and Cc2 are not connected to the LAN, andmerely have a one-to-one-type communication function by using IrDA or amodem.

As discussed above, the terminals Cs1, Cs2, Cs3, and Cs4 have both theserial communication function and the one-to-one-type communicationfunction. Accordingly, the terminals Cs1, Cs2, Cs3, and Cs4 assume therole in relaying information of the one-to-one-type communicationterminals Cc1 and Cc2 by using IrDA or a modem, and are thus referred toas “relay terminals”.

The relay terminals Cs1 and Cs4 each store a current relay situation inthe relay terminal storage unit 117. A method for registering theone-to-one-type communication terminal to which the relay terminal Cs1or Cs4 is currently providing relay services is as follows.

The user information processing unit 101 of the one-to-one-typecommunication terminal Cc1 or Cc2 sends relay request information to therelay terminal Cs1 or Cs4 via the information transmitting unit 116.

The user information processing unit 101 specifies an IrDA relayterminal with which a communication link has already been established ora relay terminal with which communication has been performed through atelephone line via a modem by dialing up a specific telephone number.Upon receiving the relay request information, the second receiving unit113 of the relay terminal Cs1 or Cs4 transmits this information to thereceived-information relay unit 119. If there is no one-to-one-typecommunication terminal to which the relay terminal Cs1 or Cs4 isproviding relay services, the received-information relay unit 119 storesID information of the one-to-one-type communication terminal which hassent the relay request information.

In this example shown in FIG. 4, when the relay terminal Cs1 receivesrelay request information from the one-to-one-type communicationterminal Cc1, and when the relay terminal Cs4 receives relay requestinformation from the one-to-one-type communication terminal Cc2, the IDinformation of the terminals Cc1 and Cc2 is registered in the relayterminal storage unit 117, as illustrated in FIG. 5.

Upon completion of registering the ID information in the relay terminalstorage unit 117, the received-information relay unit 119 reports to theone-to-one-type communication units Cc1 and Cc2 that the request hasbeen accepted by sending the corresponding information from the secondtransmitting unit 114.

If the corresponding relay terminal is already occupied with relayingfor another one-to-one-type communication terminal, a communication linkfails to be established with an IrDA relay terminal, or there is noresponse from a relay terminal using a modem. Accordingly, theone-to-one-type communication terminal searches for another relayterminal without sending relay request information.

In this manner, the terminals Cc1 and Cc2 have only a one-to-one-typecommunication function by using IrDA or a modem. However, since theterminals Cc1 and Cc2 are able to communicate with the relay terminalsCs1, Cs2, Cs3, and Cs4 by using the one-to-one-type communicationfunction, the terminal Cc1 can communicate with not only the terminalCs1, but also the terminals Cs2, Cs3, Cs4, C1, C2, and Cc2 via Cs1.Similarly, the terminal Cc2 becomes communicable with the otherterminals via the relay terminal Cs4.

If, however, the relay terminal Cs1 discontinues relay services, theone-to-one-type communication terminal Cc1 is no longer able tocommunicate with not only the terminal Cs1, but also the other terminalsCs2, Cs3, Cs4, C1, C2, and Cc2.

The other relay terminals Cs2 and Cs3 are available in the network.Thus, before discontinuing the relay services, the relay terminal Cs1reports to the one-to-one-type communication terminal Cc1 via therelay-terminal changing information transmitting unit 118 thatconnections should be changed from Cs1 to another relay terminal.

The processing executed by the relay-terminal changing informationtransmitting unit 118 when reporting the above-mentioned information tothe terminal Cc1 is as follows.

The relay terminal Cs1 sends the relay terminal information from therelay-terminal-information transmitting unit 115 via the firsttransmitting unit 111. The relay terminal information indicates the IDinformation of a relay terminal which is currently providing relayservices, in this case, Cs1, and the ID information of a one-to-one-typecommunication terminal which is currently receiving relay services, inthis case, Cc1.

Since there is no one-to-one-type communication terminal to which therelay terminal Cs2 is currently providing relay services, the relayterminal Cs2 sends relay information indicating only the ID informationCs2.

When the one-to-one-type communication function is implemented by amodem, the telephone number of the corresponding relay terminal may besent as the ID information.

Upon receiving relay terminal information from the other relayterminals, the first receiving unit 112 of the relay terminal Cs1transmits the information to the received-information relay unit 119,which then sends the information to the relay terminal storage unit 117.The relay terminal storage unit 117 determines from the relay terminalinformation the ID information of the relay terminals and the presenceor the absence of one-to-one-type communication terminals to which therelay terminals are providing relay services. If there is aone-to-one-type communication terminal which is receiving relayservices, the ID information of the one-to-one-type communicationterminal is stored. If there is no such a one-to-one-type communicationterminal, information indicating the absence of a one-to-one-typecommunication terminal is stored.

FIG. 5 shows an example of the information stored in the relay terminalstorage unit 117 of the relay terminal Cs1 according to the relaysituation shown in FIG. 4. As stated above, the relay terminal storageunit 117 stores relay terminal ID information and one-to-one-typecommunication terminal ID information. For example, when Cs1 is set inthe relay terminal ID information, and Cc1 is set in the one-to-one-typecommunication terminal ID information, the relay terminal Cs1 isproviding relay services to the one-to-one-type communication terminalCc1.

Upon receiving a relay discontinuation request from the user informationprocessing unit 101, the relay-terminal changing informationtransmitting unit 118 sends the relay-terminal changing information fromthe second transmitting unit 114. The relay-terminal changinginformation includes the ID information of an available relay terminalobtained from the relay terminal storage unit 117. If there is noavailable relay terminal, the corresponding information is sent to theone-to-one-type communication terminal.

According to the relay situation shown in FIG. 4, the relay terminal Cs1may send to the one-to-one-type communication terminal Cs1 the IDinformation of both the relay terminals Cs2 and Cs3 as therelay-terminal changing information. Alternatively, the relay terminalCs1 may send the ID information of either of the terminal Cs2 or Cs3.When the one-to-one-type communication function is implemented by amodem, the relay terminal Cs1 may send the telephone numbers of theterminals Cs2 and Cs3 as the ID information.

Upon receiving the relay-terminal changing information, the secondreceiving unit 113 of the one-to-one-type communication terminal Cc1transmits the information to the received-information relay terminal119, which then makes a request to the user information processing unit101 to change the relay terminal. When the one-to-one-type communicationfunction is implemented by using IrDA, the received-information relayterminal 119 provides the user information processing unit 101 the IDinformation of a relay terminal with which an IrDA link is established.When the one-to-one-type communication function is implemented by usinga modem, the received-information relay terminal 119 provides thetelephone number of the corresponding relay terminal.

In response to the request for changing the relay terminal, the userinformation processing unit 101 requests the designated relay terminalto relay the information of the one-to-one-type communication terminal.According to the situation shown in FIG. 4, if the relay terminal Cs2 isdesignated to take over the relay services from the terminal Cs1, theuser information processing unit 101 of the terminal Cc1 sends a relayrequest to the relay terminal Cs2. Upon accepting the relay request bythe relay terminal Cs2, the one-to-one-type communication terminal Cc1is able to continue communicating with not only the terminal Cs2, butalso the other terminals Cs3, Cs4, C1, C2, and Cc2.

A plurality of relay terminals may be designated to take over the relayservices, in which case, the one-to-one-type communication terminal mayselect one of the relay terminals.

As described above, according to the communication network systemdescribed in the first embodiment of the present invention, even if arelay terminal discontinues relay services, it informs a one-to-one-typecommunication terminal of the presence of an available relay terminal.This enables the one-to-one-type communication terminal to continuecommunicating with the other terminals by using the designated relayterminal.

In the foregoing embodiment, when the one-to-one-type communicationfunction is implemented by IrDA, the one-to-one-type communicationterminal may be unable to receive relay-terminal changing informationdue to, for example, an IrDA terminal being moved, in which case,communication may be suddenly discontinued. Likewise, communication witha relay terminal by using a modem may be discontinued due to a suddendisconnection of a telephone line.

In terms of dealing with such accidental disconnection of communication,the present invention is now described through illustration of a secondembodiment.

Second Embodiment

In the second embodiment, the aforementioned accidental disconnection ofcommunication can be overcome by sending relay terminal informationreceived by a relay terminal to a one-to-one-type communicationterminal, thereby enabling the one-to-one-type communication terminal tosend a relay request to another relay terminal.

Details of the second embodiment are discussed below with reference toFIG. 6. A relay terminal and a LAN terminal used in this embodiment areconfigured as shown in FIGS. 1 and 3, respectively. A one-to-one-typecommunication unit is configured as shown in FIG. 6 and is differentfrom the counterpart shown in FIG. 2 in that the relay terminal storageunit 117 is disposed in the communication control unit 102. As in therelay terminal of the first embodiment, the relay terminal storage unit117 stores, from the received relay terminal information, which relayterminal is providing relay services and which communication unit isreceiving them.

The processing executed by the relay terminal storage unit 117 isdescribed below according to the situation shown in FIG. 4, as has beendiscussed in the first embodiment.

The relay terminal information transmitting unit 115 of the relayterminal Cs1, Cs2, Cs3, or Cs4 regularly transmits the relay terminalinformation from the first transmitting unit 111. The relay terminalsends the relay terminal information received from the other relayterminals via the first receiving unit 112 and transmits it from thesecond transmitting unit 114 via the received-information relay unit119.

This enables a one-to-one-type communication terminal to receive therelay terminal information from all the relay terminals disposed in thenetwork via the second receiving unit 113. Then, the second receivingunit 113 sends the relay terminal information to thereceived-information relay unit 119, which then transmits only the relayterminal information to the relay terminal storage unit 117. The relayterminal storage unit 117 stores the relay terminal information, as inthat of the relay terminal of the first embodiment.

In the example shown in FIG. 4, the information stored in the relayterminal storage unit 117 of the one-to-one-type communication terminalCc1 is shown in FIG. 5, as in the information of the relay terminal Cs1of the first embodiment. However, the information stored in theone-to-one-type communication unit Cc1 differs from that stored in therelay terminal of the first embodiment in that the time at which therelay terminal information is received from each relay terminal is alsorecorded. This information is used for determining whether relayterminal information, which must be transmitted regularly, has beenreliably received in case of the occurrence of accidental communicationfailures due to a disconnection of an IrDA link or a disconnection of atelephone line via a modem.

If it is found that the received time has not been updated for a certainperiod of time in the relay terminal storage unit 117, it is determinedthat the one-to-one-type communication unit is unable to communicatewith the corresponding relay terminal. Then, the entry of the relayterminal is deleted from the relay terminal storage unit 117.

When the one-to-one-type communication unit is unable to communicatewith the relay terminal which is providing relay services for a certainperiod of time, none of the entries in the relay terminal storage unit117 is updated. In this case, it is determined that the one-to-one-typecommunication terminal is no longer able to communicate with the relayterminal. Accordingly, the period before determining that theone-to-one-type communication terminal is unable to communicate with therelay terminal is set longer than the period before determining that theentries of the other relay terminals are deleted from the relay terminalstorage unit 117.

In this example, when the one-to-one-type communication terminal Cc1determines that it is unable to communicate with the relay terminal Cs1,the relay terminal storage unit 117 of the one-to-one-type communicationterminal Cc1 sends a request for changing the relay terminal to the userinformation processing unit 101.

In this case, as in the first embodiment, both the relay terminals Cs2and Cs3 may be designated to the one-to-one-type communication terminalCc1. Alternatively, the relay terminal storage unit 117 may select oneof the designated terminals, such as the terminal whose relay terminalinformation has been updated most frequently.

According to the second embodiment of the present invention, even ifcommunication with a relay terminal is suddenly discontinued withoutbeing able to receive an instruction to change the relay terminal due tothe IrDA terminal being moved, or because a telephone line is suddenlydisconnected via a modem, a one-to-one-type communication terminal isable to request another relay terminal to continue providing relayservices.

Third Embodiment

In the first embodiment, even if a relay terminal discontinues relayservices, a one-to-one-type communication terminal is able to continuecommunicating with other terminals by making a relay request to anotherrelay terminal.

In this case, however, while the relay services are being shifted fromone relay terminal to another relay terminal, the one-to-one-typecommunication terminal is unable to receive information sent to thisterminal. In order to overcome this situation, in a third embodiment, arelay terminal which is to take over the relay services stores theinformation addressed to the one-to-one-type communication terminaluntil communication with the one-to-one-type communication terminal isrestarted.

Details of the third embodiment are discussed below with reference toFIGS. 7 through 10. A relay terminal used in the third embodiment isconfigured as shown in FIG. 7. A one-to-one-type communication terminaland a LAN terminal used in the third embodiment are configured asillustrated in FIGS. 2 and 3, respectively.

According to the relay terminal shown in FIG. 7, the communicationcontrol unit 102 is formed of the first transmitting unit 111, the firstreceiving unit 112, the second receiving unit 113, the secondtransmitting unit 114, the relay-terminal-information transmitting unit115, the information transmitting unit 116, the relay terminal storageunit 117, the relay-terminal changing information transmitting unit 118,the received-information relay unit 119, and a received-informationstorage unit 120.

The relay terminal of this embodiment differs from the counterpart ofthe first embodiment in that the received-information storage unit 120is provided. Upon receiving information addressed to the one-to-one-typecommunication terminal, the received-information storage unit 120receives the information from the received-information relay unit 119and stores it. As discussed in the first embodiment, when the relayterminal discontinues the relay services, the relay-terminal changinginformation transmitting unit 118 has the function of sending IDinformation of an available relay terminal from the relay terminalstorage unit 117 to the one-to-one-type communication terminal. An extrafunction is also added to the relay-terminal changing informationtransmitting unit 118 of this embodiment. That is, if informationindicating that a relay terminal has refused to take over the relayservices is received from the received-information relay unit 119 viathe first receiving unit 112 or the second receiving unit 113, therelay-terminal changing information transmitting unit 118 searches foranother relay terminal which can take over the relay services. If thereis a corresponding relay terminal, relay terminal taking-overinformation is sent to the one-to-one-type communication terminal. Ifthere is no available relay terminal, the relay-terminal changinginformation transmitting unit 118 reports to the one-to-one-typecommunication terminal via the first transmitting unit 111 or the secondtransmitting unit 114 that no relay terminal can take over the relayservices.

The other functions of the elements are basically similar to those ofthe elements designated with the same reference numerals and the samenames described in the first embodiment.

The process of taking over relay services by another relay terminal isdescribed below according to the situation shown in FIG. 4, as in thefirst embodiment.

It is now assumed that the relay terminal Cs1 is relaying theinformation of the one-to-one-type communication terminal Cc1. When therelay terminal Cs1 is to discontinue the relay services, the userinformation processing unit 101 of the relay terminal Cs1 notifies thecorresponding information to the relay-terminal changing informationtransmitting unit 118. Upon receiving this information, therelay-terminal changing information transmitting unit 118 transmitsrelay terminal taking-over information to the relay terminal which is totake over the relay services via the first transmitting unit 111.

The relay terminal taking-over information includes the ID informationof the relay terminal which is providing the relay services and the IDInformation of the one-to-one-type communication terminal which isreceiving the services, in this example, the ID information of Cs1 andCc1. As the relay terminal which is to take over the relay services, anavailable relay terminal having the smallest value of ID information, inthis case, Cs2, may be selected. Alternatively, any available relayterminal may be selected. It is now assumed that the relay terminal Cs2has been selected.

The first receiving unit 112 of the relay terminal which has receivedthe relay terminal taking-over information sends it to thereceived-information relay unit 119.

The received-information relay unit 119 checks for the presence of aone-to-one-type communication terminal to which the relay terminal iscurrently providing relay services by referring to storage informationof the relay terminal storage unit 117. If it is found that the relayterminal is not relaying information, the received-information relayunit 119 obtains the ID information of the relay terminal which iscurrently providing relay services and the corresponding one-to-one-typecommunication terminal from the relay terminal taking-over information,and stores the ID information of the one-to-one-type communicationterminal and the relay situation in the relay terminal storage unit 117.

The relay situation stored in the relay terminal storage unit 107 hasthe following three attributes. A first attribute is “not relaying”,which indicates that there is no one-to-one-type communication terminalto which the relay terminal is providing relay services. A secondattribute is “taking over relay services”, which represents that relayservices are being taken over from one relay terminal to another relayterminal before a relay request is made from a one-to-one-typecommunication terminal. A third attribute is “relaying”, which indicatesthat information of a one-to-one-type communication terminal is beingrelayed.

The information of the relay terminal storage unit 117 is shown in FIG.8.

Upon completing the registration in the relay terminal storage unit 117,information indicating that the relay terminal has accepted to take overthe relay services is sent via the first transmitting unit 111 to therelay terminal which is currently relaying information. In this case,the terminal Cs2 transmits the information to the terminal Cs1. If therelay terminal Cs2 has already started to provide relay services,information indicating that the terminal Cs2 has refused to take overthe relay services is sent to the terminal Cs1 via the firsttransmitting unit 111.

Upon receiving either the acceptance information or the refusalinformation, the first receiving unit 112 of the relay terminal Cs1sends the information to the relay-terminal changing informationtransmitting unit 118 via the received-information relay unit 119.

If the relay-terminal changing information transmitting unit 118receives the refusal information, it searches for another relay terminalwhich can take over the relay services. If a corresponding relayterminal is found, relay terminal taking-over information is similarlytransmitted. If there is no corresponding relay terminal, informationindicating that there is no relay terminal to take over the relayservices is reported to the one-to-one-type communication terminal.

In contrast, if the relay-terminal changing information transmittingunit 118 receives the acceptance information, it sends the relayterminal changing information to the one-to-one-type communicationterminal, as in the first embodiment.

Upon receiving the relay terminal changing information, theone-to-one-type communication terminal sends a relay request to thedesignated relay terminal, as in the first embodiment. During thisprocess, upon receiving the relay request from the one-to-one-typecommunication terminal Cc1, the relay terminal Cs2, which has acceptedto take over the relay services, changes the relay situation stored inthe relay terminal storage unit 117 from “taking over relay services” to“relaying” and starts to provide relay services. If thereceived-information relay unit 119 receives information addressed tothe one-to-one-type communication terminal Cc1 while taking over relayservices from the relay terminal Cs1, it stores the information in thereceived-information storage unit 120, and transmits it to theone-to-one-type communication terminal Cc1 via the second transmittingunit 114 at the start of providing relay services.

According to the communication network system constructed in accordancewith the third embodiment of the present invention, while relay servicesare being shifted from one relay terminal to another relay terminal,information addressed to a one-to-one-type communication terminal isstored. Then, as soon as the provision of relay services is started, thestored information is sent to the one-to-one-type communicationterminal. As a result, the information can be efficiently received bythe one-to-one-type communication terminal without losing it.

To further develop the present invention, another communication networksystem is described below through illustration of a fourth embodiment.In this network system, a central relay terminal for centrally managingthe situation of all the relay terminals is provided, and only thetelephone number of the central relay terminal is required to enable aone-to-one-type communication unit to receive relay services.

Fourth Embodiment

If the telephone number of only one relay terminal is known to aone-to-one-type communication terminal using a modem, and if the relayterminal has already begun to provide relay services to anotherone-to-one-type communication terminal, the one-to-one-typecommunication terminal is unable to receive the relay services.

To overcome this drawback, the following type of network system isimplemented in the fourth embodiment. A central relay terminal forcentrally managing the situation of all the relay terminals is provided,and then, only the telephone number of the central relay terminal isrequired to enable a one-to-one-type communication terminal to receiverelay services.

The fourth embodiment is discussed in detail below with reference toFIGS. 11 and 12. The central relay terminal used in the fourthembodiment is configured as shown in FIG. 11, while the other relayterminals are configured as illustrated in FIG. 12. A one-to-one-typecommunication terminal and a LAN terminal are configured similarly tothose of the first embodiment. The individual elements of the centralrelay terminal and the other relay terminals are similar to those of thefirst embodiment.

According to the central relay terminal, the communication control unit102 is formed of, as shown in FIG. 11, the first transmitting unit 111,the first receiving unit 112, the second receiving unit 113, the secondtransmitting unit 114, the information transmitting unit 116, the relayterminal storage unit 117, and the received-information relay unit 119.The central relay terminal is different from the relay terminal shown inFIG. 1 in that the relay-terminal-information transmitting unit 115 andthe relay-terminal changing information transmitting unit 118 are notdisposed. The other elements are basically similar to those of the relayterminal designated with the same reference numerals and the same namesshown in FIG. 1.

According to the relay terminal, the communication control unit 102 isformed of, as shown in FIG. 12, the first transmitting unit 111, thefirst receiving unit 112, the second receiving unit 113, the secondtransmitting unit 114, the information transmitting unit 116, therelay-terminal-information transmitting unit 115, and thereceived-information relay unit 119. The relay terminal shown in FIG. 12is different from the relay terminal shown in FIG. 1 in that the relayterminal storage unit 117 and the relay-terminal changing informationtransmitting unit 118 are not disposed. The other elements are basicallysimilar to those of the relay terminal designated with the samereference numerals and the same names shown in FIG. 1.

The process of designating the relay terminal which is providing relayservices to a one-to-one-type communication terminal by the centralrelay terminal is discussed below according to the situation shown inFIG. 9.

The relay terminals Cs1, Cs2, and Cs3 configured as shown in FIG. 12each transmit relay terminal information from therelay-terminal-information transmitting unit 115 via the firsttransmitting unit 111 in a manner similar to the first embodiment.

Upon receiving the relay terminal information from the relay terminalsCs1, Cs2, and Cs3 via the first receiving unit 112, the centralcommunication terminal Cm configured as shown in FIG. 11 sends theinformation to the received-information relay unit 119.

The received-information relay unit 119 stores the relay terminalinformation in the relay terminal storage unit 117 according to a methodsimilar to that discussed in the first embodiment.

In this case, the storage content of the relay terminal storage unit 117is as illustrated in FIG. 10. That is, the relay terminals Cs1 and Cs2are not providing relay services to any communication terminal. Therelay terminal Cs3 is providing relay services to a one-to-one-typecommunication terminal Cc3.

When a one-to-one-type communication terminal Cc1 is to receive relayservices, the user information processing unit 101 of the terminal Cc1first sends relay terminal inquiry information to the central relayterminal Cm via the information transmitting unit 116.

In the central relay terminal Cm, upon receiving the inquiryinformation, the second receiving unit 113 sends the information to thereceived-information relay unit 119. The received-information relay unit119 obtains ID information of available relay terminals from the relayterminal storage unit 117 and transmits it via the second transmittingunit 114 in response to the inquiry information sent from theone-to-one-type communication terminal.

In this example shown in FIG. 9, the ID information of both the relayterminals Cs1 and Cs2 may be sent, or the ID information of either ofthe terminal Cs1 or Cs2 may be selected.

The one-to-one-type communication terminal Cc1 then identifies theavailable relay terminal from the received ID information and makes arelay request to the relay terminal. With this arrangement, when theone-to-one-type communication function is implemented by using a modem,the telephone number of only the central relay terminal Cm is requiredto enable the one-to-one-type communication terminal to receive relayservices.

When the relay terminal is to discontinue relay services, the userinformation processing unit 101 of the relay terminal transmits thecorresponding information to the one-to-one-type communication unit viathe information transmitting unit 116. Then, the one-to-one-typecommunication terminal recognizes that the relay services have beendiscontinued and makes an inquiry to the central relay terminal Cmaccording to the above-described process in order to request anotherrelay terminal to provide relay services.

According to the communication network system constructed in accordancewith the fourth embodiment, even if a relay terminal discontinues relayservices, a one-to-one-type communication terminal is able to continuecommunicating with the other terminal in the network by making aninquiry to the central relay terminal Cm about a relay terminal whichcan take over the relay services.

Fifth Embodiment

In a fifth embodiment of the present invention, a relay terminal has atleast two first transmitting units 111 and two first receiving units 112similar to those of the first embodiment. In the first embodiment,information is transmitted to and received from a wireless LAN throughthe first transmitting unit 111 and the second receiving unit 112. Inthe fifth embodiment, a communication network system having not only thefunction of communicating with a wireless LAN, but also the function ofcommunicating with a cable LAN, is provided.

In a relay terminal, information received from a wireless LAN is relayedto a cable LAN and to the second transmitting unit 114; informationreceived from the cable LAN is relayed to the wireless LAN and to thesecond transmitting unit 114; and information received from the secondreceiving unit 113 is relayed to a transmitting unit of the wireless LANand to a transmitting unit of the cable LAN. It is thus possible toperform communication among wireless LAN terminals, cable LAN terminals,and one-to-one-type communication terminals, which cannot beconventionally achieved.

According to the relay terminal of the fifth embodiment, a plurality offirst transmitting units 111 and a plurality of receiving units 112 areprovided. Accordingly, the relay terminal of this embodiment differsfrom that of the first embodiment merely in the content of the relayterminal information and the function of the relay terminal storage unit117. Thus, only the above two features are explained below.

The relay terminal information includes communication devices which arereceiving relay services and the presence or the absence of suchcommunication devices. If there is any one-to-one-type communicationdevice, ID information of one-to-one-type communication terminals iscontained in the relay terminal information. It is now assumed that therelay terminal Cs1 has a function of performing one-to-one-typecommunication with a wireless LAN and a cable LAN and is relayinginformation of all the terminals. In this case, the relay terminalinformation indicates that the relay terminal Cs1 is providing relayservices to the wireless LAN, the cable LAN, and the one-to-one-typecommunication terminal Cc1. Upon receiving the relay terminalinformation, the relay terminal Cs1 stores it in the relay terminalstorage unit 117 according to a process similar to that described in thefirst embodiment.

However, according to N-to-N-type communication devices, such as awireless LAN or a cable LAN, if a plurality of terminals are providingrelay services in a single communication device, a loop is formed in thecommunication network, and the information may be relayed endlessly.Thus, each relay terminal searches the relay terminal information forterminals which are currently providing relay services in the samecommunication device, and if there is a relay terminal which has alreadystarted relay services, the corresponding relay terminal stops providingservices. The terminal which stops relay services may be determined bycomparing the ID values, in which case, either the terminal having agreater value or the terminal having a smaller value may be determined.

When the relay terminal discontinues relay services, relay services aretaken over from this terminal to another relay terminal for continuingproviding the services to a one-to-one-type communication terminalaccording to a process similar to that stated in the first embodiment.Considering the possibility of forming an endless loop described above,the information of the terminal having the smallest ID value in the samecommunication device is obtained from the relay terminal storage unit117 and only this terminal is entitled to restart relay services throughthe corresponding first transmitting unit 111 and the first receivingunit 112. Alternatively, the terminal having the greatest ID value orthe ID value closest to the ID value of the terminal which hasdiscontinued relay services may be selected. That is, any terminal maybe selected as long as only one terminal restarts relay services.

Sixth Embodiment

In a sixth embodiment of the present invention, as well as in the firstand fifth embodiments, ID information of a communication device and aterminal which are receiving relay services are provided for the relayterminal information. For example, if a terminal Cs1 has aone-to-one-type communication function with communication devices, suchas a wireless LAN, an IrDA device, and a Bluetooth device (which isdescribed in detail below), and is providing relay services to all thedevices, the relay terminal information indicates that IrDAcommunication is performed with a terminal Cc1, and Bluetoothcommunication is performed with a terminal Cbt1. Such relay terminalinformation is received and is stored in the relay terminal storage unit117 according to a process similar to that of the first embodiment. Asthe communication devices, a modem may be included.

Details of Bluetooth (hereinafter referred to as “BT”) are as follows.The BT is a wireless communication technique for use in mobile terminalsrecommended by many companies, and is targeted for the use in officesand households. By using this technique, notebook personal computers,PDAs, and cellular telephones are connected to each other without cablesso that they can exchange sound and data. By utilizing a 2.4 GHzfrequency band, which can be used without a license, communication canbe performed at approximately 1 Mbps. Unlike the IrDA technique, thedistance between devices is about 10 m, and communication can beperformed even if there is an obstacle between the devices.

When the above-described relay terminal discontinues IrDA services, theIrDA services are shifted to another relay terminal according to aprocess similar to that stated in the first embodiment. When the relayterminal stops BT services, the BT services are shifted to another relayterminal according to a process similar to that described in the firstembodiment. If both services are discontinued, both processing isperformed.

Seventh Embodiment

In a seventh embodiment of the present invention, as well as in thefifth and sixth embodiments, communication devices which are receivingrelay services and the presence or the absence of such devices areprovided for the relay terminal information. If there is anyone-to-one-type communication device, ID information of one-to-one-typecommunication terminals is contained in the relay terminal information.

For example, if the terminal Cs1 has a one-to-one-type communicationfunction of communicating with communication devices, such as a wirelessLAN, a cable LAN, an IrDA device, and a Bluetooth device, and relayinginformation of all the devices, the relay terminal information indicatesthat the relay terminal Cs1 is providing relay services to the wirelessLAN, the cable LAN, the IrDA device Cc1, and the BT device Cbt1. Suchrelay service information is received and stored in the relay terminalstorage unit 117 according to a process similar to that discussed in thefirst embodiment.

The relay services are taken over from one relay terminal to anotherrelay terminal for the LAN devices through the first transmitting unit111 and the first receiving unit 112 in a manner similar to the fifthembodiment, and for the one-to-one-type communication devices throughthe second transmitting unit 114 and the second receiving unit 113 in amanner similar to the sixth embodiment.

Eighth Embodiment

In an eighth embodiment, a relay terminal has a third transmitting unitand a third receiving unit instead of a first transmitting unit 111 anda first receiving unit 112 for use in a cable LAN, which are providedfor the fifth embodiment. The third transmitting unit and the thirdreceiving unit are able to perform only one-to-N-type communication. Theother elements and functions are similar to those of the fifthembodiment.

1. A communication network system comprising: a plurality ofcommunication terminals, each comprising: a first transmitting device;and a first receiving device, the communication terminals connected viaa transmission channel, information being transmitted and received amongsaid communication terminals through said first transmitting device andsaid first receiving device, at least two of said communicationterminals being used as relay terminals, each of said relay terminalscomprising: a second transmitting device configured to perform onlyone-to-one communication; a second receiving device configured toperform only one-to-one communication; a received-information relaydevice configured to transmit information received from said firstreceiving device to said second transmitting device, thereceived-information relay device configured to transmit informationreceived from said second receiving device to said first transmittingdevice; a relay-terminal-information transmitting device configured totransmit relay terminal information to said first transmitting device,the relay terminal information comprising terminal identificationinformation of said relay terminals and terminal identificationinformation of a terminal to which said relay terminals are providingrelay services a relay terminal storage device configured to store theterminal identification information of said relay terminal,identification information of another relay terminal and relaysituations of the relay terminals, which are acquired from the relayterminal information received from said first receiving device; and achanging device, wherein when the relay terminal which is providing therelay services discontinues the relay services, the changing devicerefers to the relay terminal storage device to determine whether anavailable relay terminal is present or absent, and if the changingdevice determines that there is an available relay terminal, thechanging device provides an instruction is to the terminal which isreceiving the relay services to change the available relay terminal. 2.The communication network system according to claim 1, wherein saidrelay-terminal-information transmitting device is configured to transmitthe relay terminal information regularly.
 3. The communication networksystem according to claim 1, wherein, when the relay terminaldiscontinues the relay services the terminal which is receiving therelay services changes from the relay terminal to the available relayterminal, and the available relay terminal then stores receivedinformation addressed to the terminal which is receiving the relayservices until a connection is established between the available relayterminal and the terminal which is receiving the relay services.
 4. Acommunication network system comprising: a plurality of communicationterminals, each comprising: a first transmitting device; and a firstreceiving device, the communication terminals connected via atransmission channel, information being transmitted and received amongsaid communication terminals through said first transmitting device andsaid first receiving device, at least one of said communicationterminals being used as a central relay terminal, and at least one ofsaid communication terminals being used as a relay terminal, said relayterminal comprising: a second transmitting device configured to performonly one-to-one communication; a second receiving device configured toperform only one-to-one communication; a first received-informationrelay device configured to transmit information received from said firstreceiving device to said second transmitting device, the firstreceived-information relay device configured to transmit informationreceived from said second receiving device to said first transmittingdevice; and a relay-terminal-information transmitting device configuredto transmit relay terminal information to said first transmittingdevice, the relay terminal information comprising terminalidentification information of said relay terminal and terminalidentification information of a terminal to which said relay terminal isproviding relay services said central relay terminal comprising: arelay-terminal storage device configured to store terminalidentification information of said relay terminal, terminalidentification information of another relay terminal and relaysituations of the relay terminals, which are acquired from the relayterminal information received from said first receiving device; and asecond received-information relay device, wherein when the central relayterminal receives from a terminalin the plurality of communicationterminals a request to provide the relay services, the secondreceived-information relay device refers to the relay-terminal storagedevice to obtain terminal identification information of an availablerelay terminal and transmits the obtained terminal identificationinformation of the available relay terminal to the terminal which makesthe request.
 5. The communication network system according to claim 1,wherein each relay terminal comprises at least two of said firsttransmitting device and at least two of said first receiving device. 6.The communication network system according to claim 1, wherein eachrelay terminal comprises at least two of said second transmitting deviceand at least two of said second receiving device.
 7. The communicationnetwork system according to claim 1, wherein each relay terminalcomprises at least two of said first transmitting device, at least twoof said first receiving device, at least two of said second transmittingdevice and at least two of said second receiving device.
 8. Acommunication network system comprising: a communication terminalcomprising: a first transmitting device; and a first receiving device; aplurality of relay terminals, the communication terminal and the relayterminals connected to each other via a transmission channel, thecommunication terminal transmitting and receiving information to andfrom the transmission channel through said first transmitting device,each of said relay terminals comprising: a second transmitting deviceconfigured to perform only one-to-one communication; a second receivingdevice configured to perform only one-to-one communication; a thirdtransmitting device configured to perform only one-to-N communication; athird receiving device configured to perform only one-to-Ncommunication, each of the relay terminals transmitting and receivinginformation to and from the transmission channel through the thirdtransmitting device and the third receiving device; areceived-information relay device configured to transmit informationreceived from said third receiving device to said second transmittingdevice, the received-information relay device configured to transmitinformation received from said second receiving device to said thirdtransmitting device; a relay-terminal-information transmitting deviceconfigured to transmit relay terminal information to said thirdtransmitting device, the relay terminal information comprising terminalidentification information of said corresponding relay terminal andterminal identification information of a terminal to which saidcorresponding relay terminal is providing relay services; a relayterminal storage device configured to store the terminal identificationinformation of said corresponding relay terminal, terminalidentification information of another relay terminal and relaysituations of the relay terminals, which are acquired from the relayterminal information received from said third receiving device; and achanging device, wherein when the corresponding relay terminal which isproviding the relay services discontinues the relay services thechanging device refers to the relay terminal storage device to determinewhether an available relay terminal is present or absent, and if thechanging device determines that there is an available relay terminal,the changing device provides an instruction to the terminal which isreceiving the relay services to change the available relay terminal. 9.A relay terminal for use in a communication network systems, whichcomprises a plurality of communication terminals, each of thecommunication terminals comprising: a first transmitting device; and afirst receiving device, the communication terminals connected via atransmission channel, information being transmitted and received amongsaid communication terminals through said first transmitting device andsaid first receiving device, one of said communication terminals beingused as said relay terminal, said relay terminal comprising: a secondtransmitting device configured to perform only one-to-one communication;a second receiving device configured to perform only one-to-onecommunication; a received-information relay device configured totransmit information received from said first receiving device to saidsecond transmitting device, and the received-information relay deviceconfigured to transmit information received from said second receivingdevice to said first transmitting device; a relay-terminal-informationtransmitting device configured to relay terminal information to saidfirst transmitting device, the terminal information comprising terminalidentification information of said relay terminal and terminalidentification information of a terminal to which said relay terminal isproviding relay services; a relay terminal storage device configured tostore the terminal identification information of said relay terminal,terminal identification information of another relay terminal and relaysituations of the relay terminals, which are acquired from the relayterminal information received from said first receiving device; and achanging device, wherein when the relay terminal which is providing therelay services discontinues the relay services, the changing devicerefers to the relay terminal storage device to determine whether anavailable relay terminal is present or absent, and if the changingdevice determines that there is an available relay terminal, thechanging device provides an instruction to the terminal which isreceiving the relay services to change the available relay terminal.